Cortex-A8 Technical Reference Manual - ARM Information Center

old Highlights interface elements, such as menu names. Denotes signal
names. Also used for terms in descriptive lists, where appropriate.
Preface
monospace Denotes text that you can enter at the keyboard, such as commands, file
and program names, and source code.
monospace Denotes a permitted abbreviation for a command or option. You can enter
the underlined text instead of the full command or option name.
monospace italic Denotes arguments to monospace text where the argument is to be
replaced by a specific value.
monospace bold Denotes language keywords when used outside example code.
< and > Angle brackets enclose replaceable terms for assembler syntax where they
appear in code or code fragments. They appear in normal font in running
text. For example:
• MRC p15, 0 , , ,
• The Opcode_2 value selects which register is accessed.
Timing diagrams
The figure named Key to timing diagram conventions explains the components used in timing
diagrams. Variations, when they occur, have clear labels. You must not assume any timing
information that is not explicit in the diagrams.
Shaded bus and signal areas are undefined, so the bus or signal can assume any value within the
shaded area at that time. The actual level is unimportant and does not affect normal operation.
Key to timing diagram conventions
Timing diagrams sometimes show single-bit signals as HIGH and LOW at the same time and
they look similar to the bus change shown in Key to timing diagram conventions. If a timing
diagram shows a single-bit signal in this way then its value does not affect the accompanying
description.
Signals
The signal conventions are:
Signal level The level of an asserted signal depends on whether the signal is
active-HIGH or active-LOW. Asserted means HIGH for active-HIGH
signals and LOW for active-LOW signals.
Lower-case n Denotes an active-LOW signal
ARM DDI 0344K Copyright © 2006-2010 ARM Limited. All rights reserved. xxiii
ID060510 Non-Confidential
Clock
HIGH to LOW
Transient
HIGH/LOW to HIGH
Bus stable
Bus to high impedance
Bus change
High impedance to stable bus